An existing infrared touch screen generally comprises an infrared tube-pair array installed on a printed circuit board around a touch detection area. The infrared tube-pair array comprises infrared emitting tubes and infrared receiving tubes. The infrared emitting tubes and the infrared receiving tubes are in a one-to-one correspondence so that the infrared receiving tubes may receive infrared light emitted by the corresponding infrared emitting tubes. When there is a touch object in the touch detection area, the light between some of the infrared emitting tubes and the corresponding infrared receiving tubes is blocked by the touch object. The infrared receiving tubes cannot receive the infrared light emitted by the corresponding infrared emitting tubes, whereby location information of the touch object may be determined according to location information of the infrared receiving tubes that cannot receive the infrared light.
For the infrared touch screen in the prior art, generally the printed circuit board installed with the infrared tube-pair array is installed in a frame. The frame's strength and flatness would maintain the circuit board's strength and flatness. Thus it is required to leave a space within the frame to accommodate the infrared tube-pair array and other electronic devices. Since there is usually a gap between the frame and at least one surface of the circuit board, the circuit board is easily deformed. Even if pressed tightly using foam, the frame and the circuit board are contacted at some points, and the frame is still prone to warping. The Chinese patent applications No. CN200620063264.2 “Outer Frame Structure for Infrared Touch Screen” and No. CN200720190699.8 “Frame for Infrared Touch Screen” disclose that there is a cavity within the frame to avoid the locations of the infrared emitting tubes, infrared receiving tubes and other electronic devices (both the infrared emitting tube and infrared receiving tube belong to the electronic device). Such the touch screen with this structure cannot adapt to current need for ultra-thin products due to increasing the thickness of the infrared touch screen. On the other hand, the printed circuit board located in the cavity is fixed only with bolts and screws locally. There is very little contact area of the framework to the printed circuit board, thereby the fixing effect is poor and the printed circuit board is prone to warping and deforming. Such the warping and deforming will cause effective light paths difficult to form between the infrared emitting tubes and corresponding infrared receiving tubes, leading to a wrong judgment for touch recognition, and may seriously cause the infrared touch screen to lose the touch recognition functionality.
In addition, in order to enable the infrared light emitted by the infrared emitting tubes to transmit through the frame of the touch screen or display to be received by the infrared receiving tubes, it is required to install a light filtering device in front of the infrared emitting tubes and infrared receiving tubes (such as light filtering sheet, also known as light transmission sheet). The light filtering device may be used for light transmission, and on the other hand, for filtering other stray light than the infrared light. In the prior art, generally there is a light transmission window on the frame and the light transmission sheet is installed in the window. Usually, the intensity of the light transmission sheet is relatively small and a special support component is needed for supporting or fixing the light transmission sheet. It is necessary for the infrared touch screen with this structure to make molds for the support component and the light transmission sheet separately, which results in high cost and complex production process and is not suitable for the ultra-thin infrared touch screens. Moreover, due to fixing the light transmission sheet, the support component must have a certain thickness, which will limit the reduction in the thickness of the touch screen.
Also, due to the limitation on the thickness of the infrared touch screen, the touch display comprising the infrared touch screen of the prior art can hardly be very thin, and cannot meet the market demands for ultra-thin super-narrow touch display.